SILICATES. 



IOI 



curve is quite different from the preceding, due in part to the higher tem- 

 perature. The absorption band at 6 ^ appears as a depression in the 

 emission spectrum. 



WOLLASTONITE (CaSi0 3 ). 



(Rod 10 mm. long, tapering from 3 to 4 mm. diameter. Energy supplied, 18 watts. 



Curves a and b, fig. 68.) 



This rod was made from a pure transparent glass, supplied by Dr. 

 Allen of the Geophysical Laboratory of the Carnegie Institution of Wash- 

 ington, which became a white crystalline mass on melting in the oxy- 

 hydrogen flame. It was rendered conducting with difficulty, and could 

 not be heated uniformly. 



2 3 4 5 



Fig. 68. Wollastonite. 



The silicate band at 2.9 p is prominent, while a new band appears at 

 3.7 p. Curve b gives the emission from the coolest side of the rod, while 

 curve a represents the emission from the hottest side. The latter is an 

 excellent illustration of the rapid increase in intensity with temperature, 



